Accelerator for the vulcanization of rubber



Patented Mar. 9, 1926.

UNITED STAT Price.

PAUL MELVIN PAULSON, ,OF PERTH AMIBOY, NEW JERSEY, ASSIGNOR TO ROES-SLER AND -HASSLAGHER CHEMICAL COMPANY, OF NEW YORK, 1\T. Y., A CORPORA-TIoN' on NEW YORK. I

ACCELERATOR FOR E vULoAnIzA'rIoN or RUBBER.

No Drawing. Original application filed February 6, 1925, Serial No.7,237. Divided and this application filed Jun v, 1925. Serial no.37,868.

To all whom it may concern:

Be it known that I, PAUL MELVIN PAUL- SON, a citizen of theUnited'States, and resident of Perth Amboy, in the county of Middlesexand State of New Jersey, have in yented certain new and usefulImprovements in Accelerators for the Vulcanization of Rubber, of whichthe following is a specification. f

The object of this invention is to provide accelerators for thevulcanization of rubber that are non-toxic, will not discolor whitearticles or bright colors, are convenient to handle-and can be readilyincorporated into the rubber mix in the mill room.

A further object of this invention is to produce a class of acceleratorswhich will bring to the finished rubber articles, inwhich they are used,superior physical properties such as higher stress strain relationship,increased tensile strength, better aging qualities and freedom fromsulphuring out or blooming.

suu another object is a; provide high I powered accelerators at lowercosts than are This invention relates to the use of those bodies formedby the interaction of'cyanamide and salts of amines'oth'er than anilineas accelerators of vulcanization fornatur'al rubber, balata,guttapercha, synthetic rubber and rubber substitutes. It. especiallyrelates to the acceleration of vulcanization of natural rubber atelevated temperatures.

I am aware that the product obtained by treating with caustic thereaction product.-

of aniline and cyanamide has heretofore been application S. N. 37,876filed June 17,

' proposed as a rubber accelerator, and make metl'iylaniline, tocyanamide form anew andv useful class of accelerators which producesuperior rubber with higher tensiles and better aging properties thanare produced by. other accelerators now in use.

' aniline, other than aniline hydrochloride, -methyl aniline, ethylaniline, the toluidines with their alkyl derivatives, Xylidine with itsalkyl derivatives, diphenylamine, and the naphthylamines upon cyana'mideby which is to be understood the unpolymerized or freecyanamide (CNNH Iprefer to use the hydrochloride salts of the above amines.

All these compounds are, characterized in that they correspond to thegeneral formula in which occurs the group This new and which is. knownas the guanidine group designation of the nitrogen atoms of guanidine onwhich the substituting'groups' occur is made following the usage asshown. in the Decennial Index of Chemical Abstracts, 1907 to 1916,subject index page 3216 under guanidine. This designation is as follows;'H N ()(zNH) -NH,

alpha beta. gamma applied to the .formulae as I have written them thisdesignation becomes =N beta nitrogen alpha nitrogen gamma nitrogen Thecompounds of my invention may also be given an amine name whichdesignates thelr method of formation as dlsclosed here;

' in. These amine names are hereafter givenin parenthesis following thename more corrmonly employed.

Compounds containing. this guanidine grouping have previously been usedas accelerators of the vulcanization of rubber butin all of thesecompounds the substituting groups have always occurred on-two orsometimes all three nitrogen atoms with the exception' of alpha monophenyl' guanidine (guanyl aniline). Thus the common *diphenyl guanidineof the art, whichv is. strictly speaking, alpha-gamma-diphenylguanidine, has the formula:

a I it/ O ulaz gAIO I g and is properly called alpha-beta-jgammaphenylguanidine.-

triphenyl guanidine or symmetrical tri I have discovered however a newclass of group or any aliphatic group,

Likewise triphenyl guanidine has the for- I accelerators in which thesubstituting groups occur on but one nitrogen atom and in that sensethey. are mono-mtrogen substituted guanidines although both hydro-' gensof the nitrogen in question may bereplaced by a substituting group. I,there'- fore, call these, in accordance with the ref- 1 erence as citedabove, alpha-substituted guanidines and as such they may have one or twosubstituting groups on the alpha nitrogen atom. It is of course obviousthat I might: arbitrarily call these gamma-sub stituted since the alphaand gamma nitrogen V mono nitrogen substituted system. I have i foundthat those materials prepared so that I R of the general formula is anaromatic group form the preferable class for the use with this asaccelerators of vulcanization, group the group R may be any aromatic orB may be any substituted aromatic group of .more than six carbon atomswhen R is hydrogen.

wherein R a substituted aromatic radical of more than six carbon atoms,1s herewith given mono orthotolyl guanidine, (guanyl ortho-toluidine)formed as follows from ortho toluidine hydrochloride and cyanamide.

These products are prepared by selecting- "the proper amine and causingit to react 'with' cyanamide. As an example of the As an example of thegeneral type RNR" =NH H1 IH wherein R- is an aromatic radical and R isOn oing-H01 d ma As an example of the general type RN-R wherein bothsubstituting groups are aro- NaOH an aliphatic radical I have preparedalpha alpha-methylphenyl guan'idine (guanyl methyl aniline) formed asfollows from mono methyl aniline hydrochloride-and cyanamid:

V ma ticI have prepared alpha-alpha-diplienyl guanidine (guanyl'diphenyl amine) from diphenyl amine hydroohlorlde and cyanamide asfollows:

- Most of these materials have low melting points, or are liquids andnone ofthem decompose at the temperatures which are used in thevulcanization of rubber arid for these reasons are much more easllycompounded than other accelerators having higher meltsome other solventwhich does not have a tendency to cause polymerization, hydrolysis,'etc.,of the free cyanamide.

Proceeding as above I have prepared "alpha mono ortho tolyl guanidine(guanyl ing points. This is a decided advantage for accelerators whichare as rapid as those which we have discovered. v

My preferred method of making these materials is as follows To asolution of one mol of unpolymerizd or free cyanamide in ethyl acetate,or other suitable solvent, is added an equivalent amount of a salt ofthe amine of the substituting group. The ethyl acetate is dis:

tilled oil and the temperature raised to from 90 to 120 (3., till thereaction is complete; The mixture is dissolved in Water and theaccelerator precipitated With caustic alkali. I have used the termcaustic or caustic alkali throughout the specification and specificallymentioned sodium hydroxide but I do not wish to be understood as havinglimited myselfto this specific base.

stance having; an alkalinity sufficiently large, as for example,potassium hydroxide, to free the organic base from the acid could beused. Onaccount, of the well knownlten'dency of free cyanamide topolymerize or other- Wise undergo changes, I prefer to use it in theform of a solution in ethyl acetate or of Any submono Xylyl guanidineortho toluidine) which is first precipitated. as an (ill and latercrystallizes to leafy" crystals having a melting point of about 46 C.The alpha inono-para tolyl' guanidine (guanyl para toluidine)precipitates in White leafy crystals of a soft silky texture having amelting point of about 68 C. The

(guanyl-l-mctaxylidine) from l-amino metaxylidine precipitates as athick oil which crystallizes very slowly on standing. The product fromdiphenyl amine, alpha-alpha-diphenyl guanidine (guanyl diphenyl amine)consists of 'fine White crystals having a melting point of tion of thesebodies I shall now describe the preparation of the orthotoluidinereaction product with free cyanamide. To 330 grams of ethyl acetatesolution of unpolymcrized or free cyanamide containing 15.8% cyanamideby analysis was added180 grams of orthotoluidine This mixture was placedin a one liter flask heated by an oil bath. The'mouth of the flask wasconnected to a condenser, a thermometer was inserted through the stopperand held in the reaction mixture. bath temperature was raised slowlytill the ethyl acetate was distilling freely and then held constant tillmost of the ethyl acetate had been distilled off. The temperature wasthen raised slowly till the reaction mixture was at 110-120 C. and thistemperature maintained for 30 minutes. The hot reaction mixture was thentaken up with 500 cc. water, poured into a 2 liter beaker and cooled toabout 15 C. It was then filtered. The filtrate was well agitated by amechanical stirrer and the beaker cooled by running tap water. 30%sodium hydroxide solution was slowly added causing a brown tinged oil toseparate. ide solution was added till no further separation of oil wasseen on further addition of caustic solution. ,The agitation with cooling was continued; in about 5'minutesthe separate oil globulescrystallized. These small balls of crystals were then easily separatedfrom the mother liquid by filtration. When dried they had a meltingpoint of 45-47? C.

The methods of carrying out my nvention with the accelerator thusproduced and other similarly produced materials -from' other amines areillustrated by the following ex 'amples:

Example lFrict'ionstacls.

Smoked sheet l 100' Zinc oxide l- 1 5 Sulphur l 5 Mono ortho tolyl'guanidine 1 \Vhen this stock is cared for 40 minutes at hydrochloride. I

The oil The sodium hydrox- 140 Q, the following properties are obtainedStretch. Permanent set. v wg gg Tensile. 782 15 1686 r 4300 .When this.same stock 'is cured for 35 min.

at 40 lbs. steam pressure and subjected to a temperature of C. for oneweek, the following results were obtained Days aged 0 1 7 600% elong1384 1843 1361 When this stock was cured for 40 mimat- 40 lbs, thefollowing results were 0btaincd:

Stretch. Permanent set. I gfii gg Tensile. 61 2 25 2325 3571 Vihen thisstock was cured 35-min. at 40 lbs;

steam pressure and subjected to the aging test as above, the followingresults were obtained 1 Days aged 0 1 7 -4=00% elong 1301 1239 1025Tensile 3170 3215 3810 'Emm ze 111. i

, I 'Parts. Smoked sheet Zinc oxide 5 Sulphur 5 Alpha-alpha-diphenylguanidine (gua- -nyldiphenyl amine) 1.25

WVhen this stock was milled and cured for 15 minutes at 40 pounds steampressure, the following results were obtained:

Stretch.

Milled andcured for 30-minutes at 10 pounds steam pressure.

' Load at i Tensile;-

Stretch. Bermanent set. 500% 91011;; I

651 15 j a 1700 lbs. 4813lbs.

: Example V.

Smoked sheet, zinc oxide and sulphur as in Example III. 1.25 partsm-xylyliguanidine (guanyl--meta xylidine).

Milled and cured for minutes at 40 pounds steam pressure.

Stretch. Permanentsct. g g Tensile.

730 20 2300lbs 5040lbs.

Those experienced in the art Willrecognize that theac'celera-torsillustrated above have manifested very excellent acceleratingproperties, and that the aging is very' s uperior as shown not only bythe-tensile strength, but also by the .fact that the stress strainrelationship'has remained-fairly constant, showing thatthe stock doesnotharden with age.

'I do not, however, wish to limit myself to the specific examples setforth above, as

v I other proportions or other formulas may be rubber. y p y 2. Aprocess of vulcamzmg rubber or sunilaranaterial which comprisescombining Q with the rubber a vulcanizing' agent and an acceleratorrepresented by the general formula R-N-H (|J=NH n-fr-n wherein R is anyaromatic group of more than six carbon atoms, and vulcanizing therubber. I

3-. A process of vulcanizingrubber or similar material which comprisescombining with the rubber a vulcanizing agent and an acceleratorrepresented by the general formula wherein R and B are dissimilar oranic groups, and vulcanizing the rubber;

l. A process of vulcanizing rubber or s1m' ilar material which comprisescombiningwith the rubber a vulcanizing agent and an acceleratorrepresented by the general formula R-N-R (3=NH H-N-H wherein R is anaromatic group and R any other organic group, and vulcanizingtherubber." p

5. A process of vulcanizing rubber or sim ilar material whichcomprisescombining with the rubber a vulcanizing agent and an acceleratorrepresented by the general formula RNR. (I1=NH H-h-H .wherein R is anaromatic group and R an aliphatic group, and vulcanizing the rubber.

6. A process of vulcanizing Tubberor Sim-- ilar material which comprisescombining with the rubber a vulcaniz'ing agent and an acceleratorcomprising a guanidine with an organic group of more than six carbonatoms substituted on the alpha nitrogen atom with hydrogen atoms on thegamma n1trogen atom, and vulcanlzmg the rubber.

. 7'. A process of vulcanizing rubber or similar' material which icomprises combining with the rubber a vulcaniz ng agent'and anaccelerator comprising a guanidine with an aromatic group ofmore thansix carbon atoms substituted on thealpha nitrogen atom with hydrogenatoms on, the gamma nitrogen atom, and vulcanizing the rubber.

8. A process of vulcanizing rubber or similar material Which comprisescombining with the rubber a vulcan-izingagent and an acceleratorrepresented by the formula R-hll C=N 1 H-N-H v and vulcanizing therubber.

.9. A process of vulcanizing rubber or similar material which comprisescombining with the rubber a vulcanizing agent and an acceleratorrepresented by the formula I H-N-H and vulcanizing the rubber.

. 10. A process of vulcamzrng a rubber mixture which comprises combiningthe rubber mixture with a vulcanizlng agent and mono ortho-t'olylguanidine and vulcanizing the mixture.

. 11. A process of vulcanizing. rubber or similar material whichcomprises combining the rubber with sulphur, zinc oxide andmono-ortho-tolyl guanidine and vulcanizing the rubber.

12. A vulcanized rubber derived from rubher or asimilar materialcombined with a vulcanizing agent and an accelerator represented by thegeneral formula -R-N-H i1=ma wherein-R is any organic group of morerubber or a similar material combined witha vulcanizing agent and anaccelerator represented by the general formula (ENE n-iv-H wherein R andR are dissimilar organic groups,

15. A vulcanized rubber derived from rubber or a similar materialcombined with a vulcanizing agent and an accelerator represented by thegeneral formula (L-Na Haawherein R is an aromatic group and R any otherorganic group.

16. A vulcanizedurubber derived from rubber or asimilar materialcombinedwith a. vulcanizing agentand an accelerator rep-' resented by thegeneral formula 50 of more than six carbon atoms substituted wherein Ris an aromatic group and R an aliphatic'group, and vulcanizing. the rubber.

-17. A vulcanized rubber or a similar material combined with avulcanizing agent and an accelerator comprising a guanidine with anorganic group of more than six carbon atoms substituted on the alphanitrogen atom with hydrogen atoms on the gamma nitrogen atom;

18. A vulcanized rubber derived from rubber or a similar materialcombined withv a vulcan z ng-age'nt and an accelerator comprising aguanidine with an aromatic group rubber derived from" on thealphafnitrogen atom with hydrogen atoms on the gamma nitrogen atom.

19. A vulcanized rubber derived from rubber or a similar materialcombined with .a vulcanizing agent and an accelerator represented by theformula CHa Belg) n-n -n I 20. A vulcanized rubber derived from rubberor a similar material combined with a a Vulcanizing agent and. an ac:elerator rep-v resented by the formula I v 21. A- vulcanized rubberderived from rubber or a similar material combined with a vulcanizingagent and mono ortho-tolyl guanidine.

22. A vulcanized rubber der ved from rubber or a simllar-materialcomblned with sulphur, zinc oxide and mono ortho-to lyl guanidine.

23.;A process of vulcanizing rubber or' similar material which comprisescombining with the rubber avulcanizing agent and au' acceleratorcomprising the product formed by treating with caustic the reactionproduct of cyanamid with a salt of. a substituted gromatic amine, andvulcanizing the ruber.

- 24. A process oir vulcanizing rubber or similar material whichcomprises combining -W1t l1' the rubber avulcamzing agentand anaccelerator comprising the product formed by treating with caustic thereaction prodnet of cyanamid with a salt of ortho toluidine, andvulcanizing the rubber.

f 25. A vulcanized rubber derived from rubber, or similar materialcombined with 'a vulcan'izing agent and an accelerator comprising theproduct formed by treating with caustic the reaction product ofcyanamidei with a salt of a substituted aromatic amine.

26. A vulcanized rubber derived from rubber or similar materialcombined. with a vulcanizing agent and an accelerator com-' prisingthe-product formed by'treating with caustic the reaction product ofcyanamide with a salt of ortho toluidine. v

Signed at Perth Arnboy, in the county of Middlesex and State of NewJersey, this firs dayof J 11116, A. D. 1925.

. PAUL MELVINPAULSON.

